Tube expanding tool having rollers confined in cage slots and inclined within range of one-fourth to two-thirds of one degree



May 20, 1958 w. E. STA 2,835,308

T EX AN ING TOOL HAVING LERS CONFINED I AG OTS AND INCLINE THIN RANGE OF ONE- RTH T0 TWO-THIRDS OF ONE DEGREE Filed July 28, 1953 2 Sheets-Sheet 1 F, G. In 2 l a.

VIIIIIIIII VI)//III'IIA INVENTOR.

563C. 01w W May 20, 1958 w. E. STARY 2,335,308

TUBE EXPANDING TOOL HAVING ROLLERS CONFINED IN CAGE SLOTS AND INCLINED WITHIN RANGE OF ONE-FOURTH TO TWO-THIRDS OF ONE DEGREE Filed July 28, 1955 2 Sheets-Sheet 2 INVENTOR. K

nite States Patent Ofitice TUBE EXPANDWG TOOL HAVING ROLLERS CON FINED TN CAGE SLOTS AND INCLINED WITH- IN RANGE OF ONE-FOURTH TO TWQ-THIRDS This invention relates to roller-type expanding tools as used to enlarge the ends of tubes to bring the tube-ends into tight engagement with their tube-holes. These expanding tools have a plurality of angularly spaced rolls confined in slots in a roll-cage and rotatably mounted about a tapered mandrel. number, have a taper of about half the mandrel taper so thata lineal portion of the tube is enlarged substantially uniformly.

Rolling and expanding tube-ends with the roller-type expanding tool cold works and thins the tube metal and causes it to flow. The tube metal flows because a compressive stress greater than the yield strength of the metal is locally produced by each of the rolls, and this stress is progressively applied by the rolling action of the tool. This action is fully described in my patent for Method and Apparatus for Expanding Tubes, Number 2,690,205.

if a force is applied at a point on the surface of a body to produce a compressive stress, the compressive stress produced is of an equal magnitude in all directions normal to the direction of the force being applied. When the force is applied so as to be equally distributed along a line of contact and applied in a rolling manner, the reaction is principally in one direction, and when such a force is applied on the inner surface of a portion of a tube, the flowing of the tube metal resulting therefrom is principally all in one direction. However, there is a small, but measurable, amount of flowing of the tube-wall metal in a direction normal to the rolling force.

When a tube-end is being rolled and expanded, the flow of tube metal which is in a direction normal to the direction of therolling action causes the portion of the tube to lengthen and to be thus extruded from the end of the tube-hole. This extrusion of the tube-wall metal is a necessary but undesirable result of the tube-rolling operation.

Fisher, Method of Joining Tubes to Headers, 2,041,915, describes this extrusion and defines it as elongation. He sets up a method for determining the proper amount of expanding by measuring this extrusion, or elongation. On page 3, column 2, lines 9 through 25, he. points out the problems encountered when rolling the The rolls, usually three in Patented May 20, 1958 The two sheets are spaced At-inch or more apart and the tube-ends are expanded into both sheets. The purpose of the two sheets is to provide a space between sheets so that a leak from either side of the assembly cannot get through the tube-joint to mix with the fluid on the other side of the tube-sheet assembly. With the double tube sheet arrangement, any leakage through a tube-joint in one of the sheets is drained oil from the space between the sheets.

Making a pressure-tight joint in each section of these tube-joints in double tube-sheets is seriously complicated by the extrusion of the tubes, if such extrusion cannot be properly directed.

Fisher, 2,041,915, describes the operation of rolling and expanding tube ends as performed with the conventional self-feeding expanding tool. This self-feeding tool has the rolls cocked so that the tapered mandrel is pulled in as the tool parts rotate. He points out that the rolled portion of the tube, when properly rolled, produces some extrusion of the tube metal in both directions, that is, out both ends of the tube-hole.

The action of the tool in producing the extruding of the tube metal from both ends of the tube-hole is complex, and the direction and amount of said extrusion from each end of the tube-hole varies with the manner in which the tool is applied to the work. Fisher, 2,041,915, inserts the expanding tool the full depth it is to engage the tube-end. With the rolls cocked at the usual self-feeding angle, the rolling force is applied at an angle which produces a component of the rolling force in an axial direction, thus tending to extrude some of the tube metal out the far end of the tube-hole. Thus the amount of tube metal extruded from the back end of the tube-hole is the sum of the axial component of the metal flow produced by the rolling action plus the metal flow produced by the yielding of the tube metal in a direction normal to the direction of the rolling force being applied. 1

While this tube-end is being rolled, the roll-cage restrains the rolls from traveling the helical path set by the cock-angle and forces the rolls to travel a circular path.

The rolls thus traveling the circular path are constantly slipping axially, and through their frictional contact, pulling the inner layer of the tube-metal toward the front end of the tube-hole, thus extruding some of the tube metal out the front end of the tube-hole.

Thus when rolling the tube-end with a self-feeding expanding tool which is restrained from moving axially, a

portion of the tube-wall metal is extruded from both ends of the tube-hole.

Sometimes the self-feeding expanding tool is allowed to travel axially as the tube-end is being rolled, similar to the travel of the rollcage of Maupin, Traveling Tube Expander, 1,514,712. When the roll-cage is allowed to travel in this manner, all of the tube-metal being extruded from the tube-hole, is extruded from the far end, the back end, of said tube-hole. The total amount of this extrusion is the sum of the metal flow produced by ends of a number of straight tubes to expand said ends.

into two headers.

Whenever a series of straight tubes are rolled and expanded into tube-holes in two end sheets, the extrusion of the tube-wall metal out the back end of the tube-holes is undesirable. This extrusion is toward the center of the tube bundle, and it produces axial loads on some of the tubes to put them under compressive-stress loading. This compressive-stress loading on the tubes tends to bow the end plates and to push loose the rolled tube-joints. This is a common problem in heat-exchangers where the tubes are closely spaced throughout all of a circular or rectangular tube-field. 7

Many heat-exchangers have double tube-sheets. This arrangement has two tube-sheets instead of a single sheet. One of the principle objects of this invention is to prothe axial component of the rolling force plus the metal flow produced by the yielding of the tube metal in a direction normal to the rolling force.

For the usual tube-joint, it is extremely difiicult to determine Where to start the tube-rolling action so that the traveling of the expander brings it to the correct final position at the precise moment the expanding is completed. Therefore the usual method is that as used by Fisher with the tool inserted full depth before the tuberolling operation is started.

Thus with the self-feeding expanding tool producing properly rolled tube-joints, there is always a considerable amount of extrusion of the tube-metal out both ends of the tube-hole.

3 vide a method for rolling and expanding tube-joints with a minimum amount of extrusion of the tube-metal.

Another object of this invention is to provide a method for rolling and expanding tube-joints so as to direct the extrusion of the tube-wall metal out the desired end of the tube-hole.

A further object of this invention is to provide tools to roll and expand tube-joints with a minimum amount of extrusion of the tube-metal and with the extrusion directed outthe desired end of the tube-holes.

Other objects and advantages of this invention will become apparent from the following description when taken in connection with the accompanying drawings, in which:

- Fig. l is a longitudinal section through a typical tubeend in its tube-hole showing the working portion of the expanding tool inserted in the tube-end in position to roil a portion of the tube-end adjacent to the end of the tube.

Fig. 2 is a cross section of the expanding tool in the tube-joint taken on the line 22 of Fig. 1.

Fig. 3a is a view showing a roll on the inside surface of the tube taken on the line 3 -3 of Pig. 2, with the roll set at a positive angle, to an exaggerated degree, to direct the elongation away from the end of the tube.

Fig. 3b is a view identical to Fig. 3a except that the roll is set at a Zero angle to divide the extrusion and direct half of it toward each end of the rolled portion of the tube.

Fig. 3c is a view identical to Fig. 3:: except that the roll is set at a negative angle to direct the extrusion toward the end of the tube.

Fig. 4 is a longitudinal section similar to Fig. 1 showing connecting parts which may be used to connect the expanding tool to a driven mechanism, not shown.

Fig. 5 is a longitudinal section through a typical. tubeend assembled in its tube-hole in a double tube-sheet with a modified form of the expanding tool inserted into the tube-end in working position to roll a portion of the tube at a point distant from the end of said tube.

Referring to the drawings, roll-cage 1, in Fig. 1, shows roll 2 in the roll-caging slot 1a, with tapered mandrel 3 inserted through said roll cage. Tube-end 5 is inserted in its tube-hole in tube-sheet S. Grooves, also called serrations, such as the two grooves 5a, are commonly used and generally considered as helping to make better tubejoints. in a properly rolled tube-joint, some of the tube metal is forced into said grooves to thus give the joint additional holding power against axial slippage and to provide additional resistance to pressure leakage by the seals at the corners of said grooves.

Fig. 2 shows a cross section of the Fig. l. expander, taken on line 2-2 of Fig. l, with the tube-end partially expanded. Tapered mandrel 3 is advanced to move rolls 2 outward radially, compressing the portions of the tubewall confined between said rolls and the surface of the tube-hole. Rolls 2 compress the wall of tube 4 over the several longitudinal areas affected by said rolls, and as these areas of high compressive stress are moved along the tube-wall by the rolling action of the tool, the portion of the tube being cold worked is enlarged.

Figs. 3a, 3b, and 3c, show various arrangements of the rolls and the resulting reactions. In each view, T shows the direction of metal-flow from the tube-metal thinning which produces the enlarging of the tube, and E" shows the direction of metal-flow in an axial direction resulting from the useful forces used to expand the tube. These reactions will be discussed in detail hereinafter.

Fig. 4 shows expander parts, similar to those in Fig. 1, inserted in a tube and tube-hole assembly together with the parts which may be used to connect said expander to a mechanism, not shown, which may be used to drive and control the action of the expanding tool.

In Fig. 4, roll-cage 1 has a threaded shank is connected to a flanged thrust-bearing member 8. Two annularly arranged series of balls 9 confine flanged-member S between the thrust faces of outer sleeve it) and back-up ring 11 so that flanged member 8 is free to rotate. Retaining ring 12 holds the assembly together and transmits the thrust reactions developed when mandrel 3 is retracted to outer sleeve 16. Coupler 13 connects the outer sleeve 16), of said thrust bearing, to frame member 314 of a driving mechanism, not shown, to thus connect roll-cage 1 of the expanding tool so that it is in a fixed axial position relative to the frame of a driving mechanism but still free to rotate.

Shank Sr of mandrel 3 seats in socket 6a of drive shaft 6 of said driving mechanism, not shown. Tang 3t on shank 3s of said mandrel seats in notch 6b in socket 6a of driving shaft 6 so that mandrel 3 is forced to rotate with shaft 6. Nut 7 connects to shaft 6 by means of the screw thread to cage shank 35 of mandrel 3 in socket 611 so that mandrel 3 is forced to move axially with shaft 6. Thus the axial movements of the driving mechanism are transmitted to the mandrel of the expanding tool to provide a separate power source which is controlled so as to control the tube expanding actions of the tool assembly.

Depth-regulating sleeve 15, in threaded engagement with shank is of roll-cage it, may be positioned at any point within its adjustment range, to control the depth of penetration of said roll-cage, to thus control the length of the tube portion being rolled. A set screw, not shown, may be used to lock sleeve 15 in any desired position.

Fig. 5 shows a modified form of the expanding tool having a roll-cage arranged for individually rolling each half of a double tube-sheet. The roll-cage 21 has rolls 22 of a length suitable for rolling the end of tube 2 4 into the tube-hole in sheet 25a or 25b. Shank 21s of roll-cage 21 may be connected to flanged-member S, of Fig. l, to connect the expanding tool of Pig. 5, through a connecting mechanism such as shown in Fig. 4, to a driving mechanism.

The depth-regulating device shown on shank 21s of roll-cage 21, in Fig. 5, allows the tool assembly to travel forward, as a portion of tube 24 is being rolled, in the following manner. Flanged member 31 is threadably connected to shank 21s so that it may be adjusted to various positions. Balls 32 are confined between the ball races of flanged member 31 and outer sleeve 33, with retaining ring 34 holding the bearing assembly together.

Thrust ring 35 is held in its forward position by spring 36. Spring 36 is preloaded sufficiently so that the normal force used to push the tool assembly into a tube to be rolled does not compress spring 36. Then, when the tube is being expanded and roll-cage 21 is rotating and traveling forward, the pulling-in force developed compresses spring 36 as flanged member 31 advances with rollcage 21.

When a tube is expanded with a self-feeding expanding tool, the operation is terminated by stopping the rotation of the tapered mandrel. Then to release the tool so that it may be moved to another tube to be rolled, the mandrel is rotated in the reverse direction, thus rotating the tool assembly backwards while the rolls travel a helical path on the mandrel to expel the mandrel and loosen the tool assembly grip in the tube.

The rolls, in a self-feeding tool, are usually cocked so that the angle a of Fig. 3a is 2 to 3 degrees. Occasionally this angle is 4 to 5 degrees, but it is never much less than 2 degrees, for the following two reasons. First, it is desirable to complete the tube expanding operation in a minimum amount of time, and the greater the angle amount of time with a not-too-great amount of the undesirable extrusion of the tube metal.

It has long been generally recognized that a self-feeding angle of less than one degree is not practical for the following two reasons. First, such a small cock-angle on the rolls pulls the mandrel forward so slowly that the roll-cage assembly rotates too many times before the tube is expanded, thus work-hardening the tube metal too severely or producing too much grain growth in said tube metal so that the tube-joints are of a poor quality. Second, at the moment the mandrel is started to rotatingin the reverse direction, to retract the expanding tool, the rolls kick by any clearance in the roll-slots to reduce the cock-angle so that the mandrel is not expelled or is expelled too slowly.

When the need for having the rolls set at a self-feeding angle is eliminated by'using a mechanism for advancing the rotating tapered mandrel, the rolls can be set at any angle desired. Mechanisms usable for this purpose include that of Lang, 1,793,624, or one such as shown in my patent for Method and Apparatus for Expanding Tubes, hereinbefore described.

Figs. 3a, 3b, and 3c, show the directions of the forces acting to thin the tube-wall with the rolls set at a positive, zero, and negative angle, respectively. The centerline of roll 2, in Fig. 3a is at a positive longitudinal angle, and the rolling force, applied by said roll, is applied at a positive tangential angle. Similarly, the centerline of roll 2, of Fig. 3c, is at a negative longitudinal angle, and the rolling force, applied by said roll, is applied at a negative tangential angle.

The magnitude of angle a of Fig. 3a, or angle 0 of Fig. 30, required to direct all of the tube extrusion in one direction, is a function of the rate of advance of the tapered mandrel, and a function of the rotating speed of the roll-cage. These two factors afiect the rate at which the tube-wall is thinned and thus affect the magnitude of the normal component acting in an axial direction and developed by the compressive and rolling forces applied on the tube metal by the rolls. Thus the more rapid the rate of doing the Work of thinning the tube-wall, the greater the angle a or fc needed to direct all of the tube-wall extrusion in one direction.

The angle necessary to direct substantially all of the extrusion in an axial direction so that it acts to elongate the tube in one direction, for average rapid work conditions, is very slight, usually about /3 of one degree. The range of this angle for the variety of types of metal currently being used for tubes and for current work-rates, as hereinbefore described, is from one-fourth of one degree to one-half and occasionally two-thirds of one degree.

Directing the extrusion so that it is all in one direction is most easily accomplished if the roll-cage assembly is allowedto travel axially as the tube-wall is thinned. Since the needed angle of cocking of the rolls is slight, the helix angle setting the rate of travel of the roll-cage is slight and the amount of axial travel of the cage assembly, occurring while the tube-wall if being thinned, is a proportionally small distance. The amount of axial travel for this type of traveling cage assembly depends upon the angle at which the rolls are set and the number of turns made by the expanding tool assembly during the tubeexpanding operation. The number of turns of the tool assembly depends upon the rate of advancing of the mandrel and the amount of thinning of the tube wall. The more rapidly the mandrel is advanced, the fewer turns to roll the tube, and conversely, the more the tube wall is thinned the more turns to roll the tube. For the average /l'll1Ch to 1-inch O. D. tube, axial travel, during the tube-rolling operation, is about Aa-inch.

For a larger diameter tube, for example a 2-inch to 3-inch O. D. tube, the axial travel would obviously be a greater amount since the pitch-distance for any given helix. angle is proportional to the I. D. of the tube, and

normally, the larger diameter tubes have an increased clearance between tube 0'. D. and tube-hole I. D., thus requiring more turns of the tool assembly to get the tubeportion thinned and enlarged. Thus for this 2-inch to 3-inch O. D. tube, the axial travel distance may be as much as or more than fii-inch.

. While, for the sake of illustration, the devices are herein shown and described in certain combinations, it will be apparent to those skilled in the art that the principles of the invention may be applicable in other combinations.

For example, the depth-regulating sleeve assembly shown in Fig. 5 may be used with roll-cage 1, shown in Fig. 4, so that roll-cage 1 may be allowed to travel in the advance direction while tube 4 is being rolled and expanded.

Depth-regulating sleeve 15, of Fig. 4, may be used with roll-cage 21, of Fig. 5, either while a tube-portion is being rolled and expanded without said roll-cage traveling, or while roll-cage 21 travels in the retracting direction while the tube-portion is being rolled.

The tool assembly shown in Fig. 5 is shown in connection with a double tube-sheet. This style of expanding tool may also be used to step-roll a tube-joint in a thick single sheet, where the length of the rolled tube-joint is too great tobe rolled and expanded in one tube-rolling operation. This thick single sheet may be one having a thickness equal to the thickness of the two tube-sheets plus the space between sheets shown in Fig. 5. The first step of the tube-rolling operation could be that of rolling and expanding the lineal portion of the tube joint, contacted by the rolls of the expanding tool, furthermost from the end of the tube. Then the expanding tool would be repositioned so that the rolls contact a lineal portion of the tube nearer to said tube-end. Usually, in this type of rolling, the rolls are positioned so as to somewhat overlap the portion of the tube-joint previously rolled.

This expanding of lineal portions .of the tube-joint is continued, step by step, until the full length of said joint is rolled and expanded. The operation can be started at the back side of the tube-sheet, with the steps progressing towards the front face of the sheet and the end of the tube, or the operation can be started at the front side of the tube-sheet, near the end of the tube, with the steps proceeding inward away from the tube-end and toward the back face of the tube-sheet.

Obvinously, it is desirable, when step rolling, to direct all extrusion of the tube metal toward the free end of the tube so that the portion of the tube-joint already rolled is not disturbed by any forces produced by the tube-metal extruding movement.

While the invention hasbeen described with reference to the particular devices illustrated, it is to be appreciated that it is not so limited. It is rather of a scope commensurate with the scope of the subjoined claims.

What I claim as my invention is:

1. A roller-type tube expanding toolhaving a rotatable tubular roll-cage, a tapered mandrel rotatable'and axially movable through the bore of the roll-cage, and a plurality of tapered, angularly spaced, rolls confined in slots through the wall of said roll-cage so as to peripherally engage the mandrel, to be rotatable, and to be radially movable, wherein the axial movements of said mandrel are produced by a separate power source with said separate power source being controlled so as to control the tubeexpanding actions of said tool assembly, and wherein said rolls are confined in said roll-cage so that their lines of contact with a circumscribing cylinder are at a longitudinal angle, said longitudinal angle being within the range of one-fourth to two-thirds of one degree, to thereby direct the tube-metal axial extrusion effects, as a lineal portion of a tube is expanded to bring it into tight enasaaaoa 2. A roller-type tube expanding tool as in claim 1; wherein said longitudinal angle is one-third of one degree.

3. A roller-type tube expanding tool as in claim 1; wherein said longitudinal angle is a positive angle.

4. A roller-type tube expanding tool as in claim 1; wherein said longitudinal angle is a negative angle.

5. A roller-type tube expanding tool as in claim 1 and including a compressible depth-regulating assembly; wherein said longitudinal angle is a positive angle, with said depth-regulating assembly providing means for positioning said tool, in said tube, a preselected distance from the end of said tube so that said rolls can travel a helical path away from said tube-end, as said tube portion is being expanded and rolled.

6. A roller-type tube expanding tool as in claim 5; wherein said positive longitudinal angle is one-third of one degree.

7. A rotatable tubular roll-cage having a plurality of angularly spaced roll-containing slots through the wall of said roll-cage, said roll-cage being for a roller-type tube expanding tool having a tapered mandrel rotatable and axially movable through the bore of said roll-cage, and a plurality of tapered rolls confined in said roll-containing slots so as to peripherally engage the mandrel, to be rotatable, and to be radially movable, wherein the axial movements of said mandrel are produced by a separate power source with said separate power source being controlled so as to control the tube-expanding actions of said tool assembly, and wherein said rolls are confined in said roll-cage so that their lines of contact with a circumscribing cylinder are at a longitudinal angle, said longitudinal angle being within the range of onefourth to two-thirds of one degree, to thereby direct the tube-metal axial'extrusion effects, as a lineal portion of a tube is expanded to bring it into tight engagement in its cooperating assembly member, so that a minimum amount of extrusion is produced with all of said extrusion being in one direction.

8 8. A rotatable tubular roll-cage as in claim 7; wherein said longitudinal angle is one-third of one degree.

9. A rotatable tubular roll-cage as in claim 7; wherein said longitudinal angle is a positive angle.

10. A rotatable tubular roll-cage as in claim 7; wherein said longitudinal angle is a negative angle.

References Cited in the file of this patent UNITED STATES PATENTS 941,190 Didier Nov. 23, 1909 1,514,712 Maupin Nov. 11, 1924 1,516,704 Braun Nov. 25, 1924 1,680,922 Wiedeke Aug. 14, 1928 1,793,624 Lang e Feb. 24, 1931 1,798,442 Wiedeke Mar. 31, 1931 1,873,568 Ford Aug. 23, 1932 2,041,915 Fisher May 26, 1936 2,045,787 Maupin June 30, 1936 2,085,447 Plaine June 29, 1937 2,219,784 Maupin Oct. 29, 1940 2,373,097 Boyles Apr. 10, 1945 2,375,235 Maxwell May 8, 1945 2,448,512 Brackett Sept. 7, 1948 2,546,756 Knowlton Mar. 27, 1951 2,630,853 Toth Mar. 10, 1953 2,649,889 Dudley Aug. 25, 1953 2,690,205 Stary Sept. 28, 1954 2,736,950 Mathews Mar. 6, 1956 2,737,996 Toth Mar. 13, 1956 FOREIGN PATENTS 19,788 Great Britain Oct. 4, 1901 377,465 France July 11, 1907 525,549 Germany May 26, 1931 47,248 Denmark Apr. 24, 1933 602,215 Germany Sept. 4, 1934 

